System and method for removing or installing a main shaft of a wind turbine with a push/pull system configured at an end of the main shaft

ABSTRACT

A method and system for removing or installing a main shaft and attached main bearing assembly of a wind turbine from a bedplate installed atop a wind turbine tower using an assist motive system configured at a downwind end of the main shaft to push or pull the main shaft out of or into the bedplate.

FIELD OF THE INVENTION

The present disclosure relates generally to wind turbines, and moreparticularly to systems and methods for removing and/or installing amain shaft to and from a nacelle located atop a wind turbine tower.

BACKGROUND OF THE INVENTION

Wind power is considered one of the cleanest, most environmentallyfriendly energy sources presently available, and wind turbines havegained increased attention in this regard. A modern wind turbinetypically includes a tower, a generator, a gearbox, a nacelle, and oneor more rotor blades. The nacelle includes a rotor assembly coupled tothe gearbox and to the generator. The rotor assembly and the gearbox aremounted on a bedplate support frame located within the nacelle. In manywind turbines, the gearbox is mounted to the bedplate via one or moretorque supports or arms. The rotor blades capture kinetic energy of windusing known airfoil principles and transmit the kinetic energy in theform of rotational energy so as to turn a main shaft coupling the rotorblades to the gearbox, or if a gearbox is not used, directly to thegenerator. The generator then converts the mechanical energy toelectrical energy that may be deployed to a utility grid.

More specifically, the majority of commercially available wind turbinesutilize multi-stage geared drivetrains to connect the turbine blades toan electrical generator. The wind turns the turbine blades, which spin alow speed shaft, i.e. the main shaft. The main shaft is coupled to aninput shaft of a gearbox, which has a higher speed output shaftconnected to a generator. Thus, the geared drivetrain aims to increasethe velocity of the mechanical motion. Further, the gearbox and thegenerator are typically supported by one or more bearings and mounted tothe bedplate via one or more torque arms or supports.

Over time, the main shaft and associated bearings may become worn and/ordamaged due to loads and forces from the wind acting on the wind turbinecomponents. Unfortunately, repair of the main shaft and/or the mainbearing assembly often requires the turbine head (machine head) to beremoved from atop the nacelle and transported to a factory wherein thebedplate is stood up vertically to remove the main shaft and bearingassembly, which is a very time-consuming and expensive procedure.

U.S. Pat. No. 8,696,302 discloses a method for repairing or replacing amain bearing on a wind turbine without removing the rotor and mainshaft. This method is not suited for wind turbine designs whereinbearing replacement or repair requires removal of the rotor and mainshaft.

U.S. Pat. No. 8,108,997 discloses a method for stabilizing the mainshaft within the bedplate on a single bearing unit to repair or replacethe gear box. This method is not suited for a procedure that requiresremoval of the rotor and main shaft to replace or repair the mainbearing assembly.

To date, there has been no viable method for repairing, replacing, orupgrading a dual main bearing unit seated in a bedplate uptower in thefield wherein the procedure requires removal of the rotor and main shaftfrom the bedplate.

Thus, the industry is in need of new and improved systems and methodsfor repairing, replacing, or upgrading the main shaft bearing seated inthe bedplate of the wind turbine in the field, wherein the bedplateremains installed in a horizontal position atop the tower, or is removedfrom the tower in the field.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

In one aspect, the present invention is directed to a system and methodwherein an assist motive system is configured at the downwind end of themain shaft to facilitate pulling or pushing of the main shaft into ourout of the bedplate

In this regard, a method is provided for removing an installed mainshaft and attached main bearing assembly of a wind turbine from abedplate in the field, wherein a rotor has been removed from an upwindend of the main shaft, a downwind end of the main shaft has beendisconnected from a gearbox, and the gearbox has been removed from thebedplate. The method includes supporting the upwind end of the mainshaft with a rigging system that is suspended from a crane. An assistsystem is fixed to the downwind end of the bedplate and used to push thedownwind end of the main shaft partway through the bedplate, wherein themain shaft at the downwind end is supported on a bearing unit fixed inthe bedplate and the main shaft at the upwind end is supported by therigging system. With the crane, the method includes supporting theupwind end of the main shaft to unload the bearing unit and slide themain shaft out of the bedplate until the downwind end is free of thebearing unit. With the crane fully supporting the main shaft, the craneis used to horizontally slide the main shaft out from the bedplate. Theassist system can be disconnected from the downwind end of the mainshaft before or after the bearing unit is unloaded.

The assist system can have various configurations within the scope andspirit of the invention, and can be any one or combination of electric,hydraulic, pneumatic, electro/hydraulic, or other conventional systemconfigured to apply a push and/or pull force to the downwind end of themain shaft. In a particular embodiment, the assist system is a hydraulicram assembly in a push configuration, and the method includesconfiguring multiple hydraulic cylinders with rams at the downwind endof the main shaft in a manner to apply a uniform pushing force to thedownwind end of the main shaft.

In a certain embodiment, the hydraulic ram assembly may include a platethat bears directly or indirectly against the downwind end of the mainshaft, with the hydraulic cylinders and rams configured to apply thepushing force to the plate.

The main shaft may have a main bearing assembly fitted thereon adjacentthe upwind end of the main shaft, wherein the hydraulic ram assembly hasa push stroke sufficient to unseat the main bearing assembly and push acenter of gravity of the main shaft and main bearing assembly out fromthe upwind end of the bedplate.

An embodiment of the method may further include fixing a ring to thedownwind end of the bedplate around the main shaft, and fixing a rod tothe ring for each hydraulic cylinder. The hydraulic cylinders and plateslide onto to the rods in an orientation such that the rams bear againststops on the rods and the cylinders are mounted to the plate.

The present invention also encompasses a method for installing a mainshaft and attached main bearing assembly for a wind turbine in abedplate in the field, wherein a gearbox has been removed from thebedplate. The installation method includes connecting a rigging systemto an upwind end of the main shaft, the rigging system suspended from acrane. With the crane, the main shaft is fully supported and movedthrough the bedplate until a downwind end of the main shaft ispositioned at a bearing unit fixed in the bedplate adjacent the downwindend of the bedplate. An assist system is fixed to the downwind end ofthe bedplate in a pull configuration, and the method includes pullingthe downwind end of the main shaft from the bedplate until the mainbearing assembly fixed to the main shaft is seated in the bedplate, themain shaft supported by the bearing unit as it is pulled by the assistsystem.

The aspects of the assist system discussed above with respect to themain shaft removal method are applicable to the installation method aswell.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIG. 1 is a perspective view of a conventional wind turbine;

FIG. 2 is a perspective view of a simplified, internal view of oneembodiment of a nacelle of a conventional wind turbine;

FIG. 3 is a perspective view of one embodiment of a drivetrain assemblyparticularly illustrating the main shaft and main bearing assembly;

FIG. 4 is a perspective view of initial steps for pulling the main shaftfrom the wind turbine bedplate in accordance with aspects of theinvention;

FIG. 5 is a perspective view of additional steps for pulling the mainshaft from the wind turbine bedplate;

FIG. 6 is a perspective view of still further steps for pulling the mainshaft from the wind turbine bedplate;

FIG. 7 is a perspective view of additional steps for pulling the mainshaft from the wind turbine bedplate;

FIG. 8 is a perspective view of the main shaft removed from the bedplateand supported by a crane;

FIG. 9 is a perspective view of a main shaft prior to installation ofsupport elements thereon;

FIG. 10 is a perspective view of the main shaft of FIG. 9 with thesupport elements installed on the downwind end thereof;

FIG. 11 is a diagram view of a main shaft with support elements todefine a cylindrical extension region on the downwind end of the mainshaft;

FIG. 12 is a perspective view of the outer ring member of the supportelements;

FIG. 13 is a perspective view of the inner ring member of the supportelements;

FIG. 14 is a perspective view of the support ring member of the outersupport elements;

FIG. 15 is a perspective view of a hydraulic ram assembly in a pushconfiguration for pushing the downwind end of the main shaft through thebedplate;

FIG. 16 is a perspective view of the hydraulic ram assembly of FIG. 15at the end of its push stroke;

FIG. 17 is a perspective view of the hydraulic ram assembly in a pullconfiguration for pulling the downwind end of the main shaft into thebedplate;

FIG. 18 is a perspective view of the hydraulic ram assembly of FIG. 17at the end of its pull stroke;

FIG. 19 is a flow chart of a method embodiment for removal of the mainshaft from the wind turbine bedplate; and

FIG. 20 is a flow chart of a method embodiment for installation of themain shaft in the wind turbine bedplate.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

Generally, the present invention is directed to methods for installationand/or removal of the main shaft (with attached main bearing assembly)from a bedplate (e.g., a single piece forged bedplate) in the field,wherein the nacelle (machine head) remains atop the tower or is removedfrom the tower for servicing at ground level in the field. The methodsprovide significant commercial advantages in terms of time and expensefor maintenance procedures that require removal of the main shaft fromthe machine head, such as repair/replacement of the main bearingassembly fitted on the shaft. Aspects of the present inventive methodsare described below with reference to the drawings.

Referring now to the drawings, FIG. 1 illustrates a perspective view ofone embodiment of a wind turbine 10 relevant to the present discussion.As shown, the wind turbine 10 generally includes a tower 12 extendingfrom a support surface 14, a nacelle 16 (also referred to as a machinehead) mounted on the tower 12, and a rotor 18 coupled to the nacelle 16.The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22coupled to and extending outwardly from the hub 20. For example, in theillustrated embodiment, the rotor 18 includes three rotor blades 22.However, in an alternative embodiment, the rotor 18 may include more orless than three rotor blades 22. Each rotor blade 22 may be spaced aboutthe hub 20 to facilitate rotating the rotor 18 to enable kinetic energyto be transferred from the wind into usable mechanical energy, andsubsequently, electrical energy. For instance, the hub 20 may berotatably coupled to an electric generator 24 (FIG. 2) positioned withinthe nacelle 16 to permit electrical energy to be produced.

The wind turbine 10 may also include a wind turbine controller 26centralized within the nacelle 16. However, in other embodiments, thecontroller 26 may be located within any other component of the windturbine 10 or at a location outside the wind turbine. Further, thecontroller 26 may be communicatively coupled to any number of thecomponents of the wind turbine 10 in order to control the componentsthereof. As such, the controller 26 may include a computer or othersuitable processing unit. Thus, in several embodiments, the controller26 may include suitable computer-readable instructions that, whenimplemented, configure the controller 26 to perform various differentfunctions, such as receiving, transmitting and/or executing wind turbinecontrol signals and/or performing the various method steps as describedherein.

Referring now to FIG. 2, a simplified, internal view of one embodimentof the nacelle 16 shown in FIG. 1 is illustrated, particularlyillustrating the drivetrain assembly 30. As shown, the drivetrainassembly 30 includes the generator 24, which may be coupled to the rotor18 for producing electrical power from the rotational energy generatedby the rotor 18. The rotor 18 includes a main shaft 34 coupled to thehub 20 via a rotor flange 36 for rotation therewith. The main shaft 34,in turn, is rotatably coupled to a generator shaft 54 of the generator24 through a gearbox 38 connected to a bedplate support frame 40 bytorque support arms 52. The bedplate 40 is depicted in the figures, forillustrative purposes, as a single-piece bedplate made from one completecasting with bores machined therein where the bearings are seated. Thepresent invention may also have utility with a two-piece bedplate thatis split horizontally, particularly if the invention offers a time andexpense advantage as compared to unbolting the split bedplate andlifting the main shaft and bearings from the bottom half of thebedplate.

Referring to FIG. 3, the main shaft 34 is supported by one or morebearing assemblies 46, 48. For example, as shown, a forward “upwind” end42 of the shaft 36 is supported by the main bearing assembly 46, whichin this particular embodiment is depicted as a double taper-rollerbearing (TRB) assembly (the main bearing assembly 46 in the embodimentof FIGS. 9 and 10 is a single taper-roller bearing). This main bearingassembly 46 is fitted onto the main shaft 36 and can only be replaced orrepaired by pulling the main shaft 34 from the bedplate 40. The aft“downwind” end 44 of the main shaft 36 is supported by the bearing unit48, which in this particular embodiment is depicted as a cylindricalroller bearing (CRB) assembly. The CRB assembly 48 is mounted to thebedplate 40, and the shaft is able to be slid axially through thisbearing 48 upon being pulled from the bedplate 40.

As is generally understood, the main shaft 34 may provide a low speed,high torque input to the gearbox 38 in response to rotation of the rotorblades 22 and the hub 20. The gearbox 38 may then be configured toconvert the low speed, high torque input to a high speed, low torqueoutput to drive the generator shaft 36 and, thus, the generator 24.

Each rotor blade 22 may also include a pitch adjustment mechanism 60configured to rotate each rotor blade 22 about its pitch axis 28.Further, each pitch adjustment mechanism 60 may include a pitch drivemotor 68 (e.g., any suitable electric, hydraulic, or pneumatic motor), apitch drive gearbox 62, and a pitch drive pinion 64. The pitch drivemotor 68 is coupled to the pitch drive gearbox 62 to impart a mechanicalforce to the pitch drive gearbox 62. Similarly, the pitch drive gearbox62 is coupled to the pitch drive pinion 64 for rotation therewith. Thepitch drive pinion 64 is in rotational engagement with a pitch bearing66 coupled between the hub 20 and a corresponding rotor blade 22 suchthat rotation of the pitch drive pinion 64 causes rotation of the pitchbearing 66, thereby rotating the rotor blade 22 about the pitch axis 28.Similarly, the wind turbine 10 may include one or more yaw drivemechanisms 56 communicatively coupled to the controller 26, with eachyaw drive mechanism(s) 56 being configured to change the angle of thenacelle 16 relative to the wind (e.g., by engaging a yaw bearing 58 ofthe wind turbine 10).

FIG. 19 provides a flowchart representation of a method embodiment 100in accordance with the present invention for removing an installed mainshaft 34 and attached main bearing assembly 46 from the bedplate 40 inthe field with the nacelle 16 remaining attached to the tower 12, orremoved from the tower and placed at ground level for servicing. Step102 involves preparing the wind turbine 10 for removal of the main shaft34. This may include any one or combination of removing the blades 22and rotor hub 20, removing various panels/wall of the nacelle 16 toexpose the bedplate 40, removing the generator 24, removing the gearbox38, arranging a crane 78 (FIG. 8) at the site, staging a rigging system70, and any other preparatory step or procedure that is necessitated bythe wind turbine design or site location for a subsequent removal of themain shaft 34. Although it may be desired for space and safety concerns,the method 100 may be practiced without removing the generator 24 incertain wind turbine designs.

At step 104, part of the rigging system 70 is connected to the upwindend 44 of the main shaft 34. For example, referring to FIG. 4, therigging system 70 may include multiple “legs” 72, 74 in the form ofchains, cables, webbing, slings, and the like, attachable to a cable onthe crane 78 by any suitable conventional means (e.g., a turnbuckle).One or more of these legs 72, 74 are connected to the upwind end 42 in amanner sufficient for the crane to support the full load of the upwindend 42 without the upwind end 42 rolling. In the depicted embodiment,the first leg 72 and second leg 74 are connected (e.g., usingturnbuckles or other suitable devices) to preexisting holes in the rotorflange 36 at upper, opposite sides of the flange 36.

Once the rigging is connected to the crane cable and the upwind end 42of the main shaft 34 is supported, step 106 involves pushing thedownwind end 44 of the main shaft 34 at least partway through thebedplate 40. This “pushing” may be accomplished by electrical,hydraulic, pneumatic, or electro/hydraulic motive means. In theembodiment of FIGS. 15-18, a hydraulic ram assembly 82 is configured atthe downwind end 44 for this purpose, as explained in greater detailbelow.

FIG. 5 depicts the upwind end 42 of the main shaft 34 being pushed outof the bedplate 40 to the extent that the main bearing assembly 46(e.g., the TRB assembly) has been unseated and is partially out of thebedplate 40.

At step 108, the main shaft 34 is slid through the bedplate 40 at leastuntil a center of gravity of the main shaft 34 and main bearing assembly46 are free of the bedplate 40, as depicted in FIG. 6. The axiallocation of the center of gravity is predefined and will vary dependingon the size of the mains shaft, the main bearing assembly, materials,and so forth.

At step 110, a “leveling” leg 76 of the rigging system 70 is attached tothe main shaft 34 at a location such that the center of gravity islocated between the leveling leg 76 and the first and second legs 72, 74of the rigging system 70. The leveling leg 76 is preferably adjustable(manually or remotely) for balancing the main shaft 34. In this manner,the main shaft 34 can be balanced and eventually fully supported by thecrane 70 in an essentially horizontal orientation (FIG. 8). In thedepicted embodiment, the leveling leg 76 is depicted as an adjustablesling or cradle that wraps around the main shaft 34. Any suitablerigging device that supports the main shaft at the desired axiallocation may be used for this purpose.

At step 112, with the crane 70, the main shaft 34 is fully supported tounload the bearing unit 48 at the upwind side 42 of the bedplate. Themain shaft 34 can then be slid completely out of the bedplate 40 withthe crane 78 (step 114), until the downwind end is free of the bearingunit 48, as depicted for example in FIG. 8. The main shaft 34 and mainbearing assembly 46 are supported by the rigging system in a horizontaland balanced orientation during this process.

At this point, at step 116, the main shaft 34 and attached main bearingassembly 46 can be lowered to the ground, at which timerepair/replacement of the main bearing assembly 46 can be done.

With certain main shaft designs, it may be desired to increase theeffective length of the downwind end 44 of the main shaft 34 to ensurethat the downwind end is supported by the bearing unit 48 at least untilthe center of gravity of the main shaft 34 and bearing assembly 46 arefree of the upwind end 42 of the bedplate 40. Referring to the view inFIG. 8, this may be accomplished by essentially adding extension orsupport elements 90 to the end of the main shaft 34 in order to extendthe cylindrical length of the shaft, as explained in more detail belowwith reference to FIGS. 9 through 14.

Referring to FIG. 20, the present invention also encompasses a method200 for installing a main shaft 34 and attached main bearing assembly 46for a wind turbine 10 in a bedplate 40 installed atop a wind turbinetower 12 in the field, wherein a gearbox 38 has been removed from thebedplate 40. The installation method 200 is essentially the reverse ofthe removal method 100.

At step 202, necessary preparations are made to the wind turbine for theinstallation.

At step 204, at least a first leg 72 of the rigging system 70 isconnected to the upwind end 42 of the main shaft 34, which may be atground level. The leveling leg 76 of the rigging system 70 is connectedto the main shaft 34 at a location such that a center of gravity of themain shaft 34 and bearing assembly 46 is located between the levelingleg 76 and the first/second legs 72, 74 of the rigging system 70. If notyet done, the rigging system 70 is connected to the crane cable, and themain shaft 34 is raised in a balanced, horizontal orientation.

At step 206, with the crane 78 fully supporting the main shaft 34, themain shaft 34 is slid through the bedplate until the downwind end 44 ofthe main shaft is positioned at the bearing unit 48 fixed in thebedplate 40.

At step 208, the load of the downwind end 44 is transferred to thebearing unit, and at step 210, the leveling leg 76 is removed from themain shaft 34 so that the mains shaft can be pulled into the bedplate40.

At step 212, the downwind end 44 is “pulled” to further slide the mainshaft into the bedplate 40 until the main bearing assembly 46 is seated.The pull system hydraulic ram assembly 82 discussed above, or other pullsystem means, can be operated in reverse for this purpose, or any othersuitable electrical, hydraulic, or electric/hydraulic system may be usedfor this purpose.

At step 214, the remaining legs 72, 74 of the rigging system 70 can beremoved from the main shaft 70. The shaft can be slide further into thebedplate 40 with the hydraulic ram assembly 82 if needed.

As discussed, the effective length of the downwind end 44 of the mainshaft 34 may be increased, for example by the addition of the supportelements 90, to ensure that the downwind end 44 is supported by thebearing unit 48 prior to pulling the downwind end 44 of the main shaft34.

Operation of one embodiment for pushing the main shaft 34 from thedownwind end 44 thereof in the removal method 100, and pulling the mainshaft 34 at the downwind end 44 in the installation method 220, isdepicted in FIGS. 15 through 18, in which FIG. 15 depicts the assistsystem as a hydraulic ram assembly 82 in a “push” configuration.Initially, a specifically designed ring or partial arc component 85 ismounted to the bedplate 40 around the main shaft 34 at the downwind end44. A plurality of rods 86 (depending on the number of hydrauliccylinders used) are threaded into this ring at equally circumferentiallyspaced locations. These rods 86 may be threaded along the lengththereof. In the depicted embodiment, three rods 86 are spaced around thering 85. A plate 88 is designed with holes corresponding to thelocations of the rods 86 on the ring 85, wherein the plate is slidableonto the rods 86. The plate 88 can have any shape, such as circular. Inthe depicted embodiment, the plate 88 is star-shaped with an arm atleach of the rod 86 locations.

Referring to FIGS. 15 through 18, a hydraulic cylinder 84 is mounted onthe plate 88 at each hole location. In the depicted embodiment, thehydraulic cylinders 84 are single acting “hollow” cylinders and mountedon the plate 88 such that a ram 87 of each cylinder 84 moves in adirection away from the plate 88 when actuated. At each location, therod 86 runs through the cylinder 84 and ram 87. Suitable hydrauliccylinders 84 are commercially available from different manufacturers,including ENERPAC.

In the push configuration of FIGS. 15 and 16, the plate 88 and hydrauliccylinders 84 are slid onto the rods 86 such that the plate 88 bearsagainst the downwind end 44 of the main shaft 34 or an end support ring94 (discussed below) attached to the end of the main shaft 34. Theposition of the rams 87 on the rods 86 is locked in place by a nutthreaded onto the rods 86 against which the rams 87 bear upon actuationof the cylinders 84. Other locking devices on the rods 86 can be usedfor this purpose. FIG. 15 depicts an initial position of the hydraulicram assembly 82 in the push configuration, and FIG. 16 depicts a finalposition wherein the plate 88 has “bottomed out” against the ring 85 andthe main shaft 34 has been pushed into the bedplate 40. The push strokeof the hydraulic cylinders 84 is thus equal to effective displacementdistance of the rams 87. Prior to downwind end 44 of the main shaft 34reaching the position depicted in FIG. 16, the main bearing assembly 46has unseated from the bedplate 40 and the leveling leg 76 of the riggingsystem has been attached to the main shaft, as depicted in FIG. 6.

FIG. 17 depicts the hydraulic ram assembly 82 configured in a “pull”configuration for pulling the downwind end 44 of the main shaft throughthe bedplate 40 for the installation method 220 described above. In thedepicted embodiment, the hydraulic rams 84 are single action rams asdiscussed above. Thus, in the pull configuration, the orientation of theplate 88 and hydraulic cylinders 84 on the rods 86 is reversed ascompared to FIG. 15 such that the rams 87 act against the ring 85 andthe hydraulic cylinders 84 (and attached plate 88) are locked inposition by stops (e.g., nuts) on the rods 86. An inner plate 89 (a“pull” plate) may be fixed to the downwind end 44 of the main shaft 34(or end support ring 94) to provide a better surface for fixing theplate 88 relative to the main shaft 34.

FIG. 17 depicts the hydraulic ram assembly 82 as it is being configuredin the pull position, and FIG. 18 depicts the hydraulic ram assembly 82and main shaft 34 at the end of the pull stroke of the hydrauliccylinders 84, wherein the main shaft 34 assumes a final position in thebedplate 40 corresponding to FIG. 4 where the main bearing assembly 46is seated at its operation position within the bedplate 40. At thispoint, the hydraulic ram assembly 82 can be dismantled from the mainshaft 34 and the support elements 90 removed.

The assist motive system is illustrated in the figures as the hydraulicram assembly 82 for illustrative purposes only. As mentioned, the assistsystem may be any one or combination of an electrical, hydraulic,pneumatic, or electro/hydraulic system configured in a push mode at thedownwind end of the main shaft.

An embodiment of the means used to extend the cylindrical profile of themain shaft 34 to ensure that the end of the main shaft 34 remains fullysupported by the bearing unit 48 at the downwind end 44 of the bedplate40 until load is transferred fully to the crane 78 is the supportelements 90 discussed above and depicted in greater detail in FIGS. 9through 12.

FIG. 9 depicts an embodiment of a main shaft 34 with a main bearingassembly 46 fitted thereon adjacent the upwind end thereof. At thedownwind end 44 it can be seen that the main shaft 34 tapers radiallyinward just aft of the bearing surface 91 that engages the bearing unit48 when the main shaft 34 is configured in the bedplate 40. Without thesupport elements 90 fitted onto this section of the main shaft 34, whenthe bearing surface 91 is pushed past the bearing unit 48, the shaftwould “drop” to a certain degree onto the radially reduced aft sectionand cant to a non-horizontal orientation within the bedplate 40, makingfurther removal of the mains shaft difficult. The opposite action wouldoccur upon installation of the shaft without the support elements 90.

The support elements 90 essentially define an extension 92 (FIG. 10)along the radially reduced aft section of the main shaft 34 that ensuresthe end of the main shaft 34 remains fully supported on the bearing unit48 in a horizontal orientation of the main shaft 34 until the full loadof the mains shaft 34 and main bearing assembly 46 is borne by therigging system 70 and crane 78. This extension 92 may be, for example, afull cylindrical extension that completely encircles the main shaft 34,or a partial semi-circular extension around a bottom portion of the mainshaft 34. The extension 92 may have a continuous surface, or adiscontinuous surface (e.g., a cage-like structure). The extension couldbe defined by one or more axially extending planks or strip members. Itshould be appreciated that various support element 90 designs can beconfigured to meet the need for supporting the end of the main shaft 34on the bearing unit 48. The cylindrical support elements 90 and fullcylindrical extension 92 illustrated in the present figures is forillustrative purposes only.

In the depicted embodiment, the support elements 90 include one or morecylindrical rings 96, 98 that slide onto or are fitted onto the mainshaft 34 around the reduced diameter section thereof. For example, aninner support ring 96 (FIGS. 11 and 13) may have a tapered innerdiameter (or other non-cylindrical profile) at one end thereof thatessentially matches the taper (or other profile) on the main shaft 34,as depicted in FIG. 11, thereby extending the cylindrical extension 92to include the tapered region of the main shaft 34. An adjacent outersupport ring 98 may be fitted onto the shaft 34 and extend essentiallyto the downwind end 44 thereof.

It should be appreciated that the inner and outer support rings 96, 98could be replaced by a single ring, a partial arc, or any combinationthereof.

The support elements 90 may also include an end support ring 94 (FIGS.11 and 14) that bolts to the downwind end 44 of the main shaft andextends the cylindrical extension 92 past the downwind end 44, as can beappreciated from FIG. 11. The end support ring 94 may have a diameterthat matches the diameter of the main shaft 34 with inner and outerrings 96, 98 fitted thereon.

It should be appreciated that a single support element 90 configured asan end-cap 93 could also serve all of the functions of the rings 94, 96,and 98, as depicted in the alternative in FIG. 11. The end-cap 93 can beformed as an integral or multi-component element with an end ringsection 95 and a cylindrical wall section 97.

The various support elements 90 may be formed of a material having a lowcoefficient of friction, yet sturdy enough to support the main shaft 34on the bearing unit 48 without significant deformation.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A method for removing an installed main shaft andattached main bearing assembly of a wind turbine from a bedplate in thefield, wherein a rotor has been removed from an upwind end of the mainshaft, a downwind end of the main shaft has been disconnected from agearbox, and the gearbox has been removed from the bedplate, the methodcomprising: supporting the upwind end of the main shaft with a riggingsystem, the rigging system suspended from a crane; with an assist systemfixed to the downwind end of the bedplate, pushing the downwind end ofthe main shaft partway through the bedplate, wherein the main shaft atthe downwind end is supported on a bearing unit fixed in the bedplateand the main shaft at the upwind end is supported by the rigging system;with the crane, supporting the upwind end of the main shaft to unloadthe bearing unit and slide the main shaft until the downwind end is freeof the bearing unit; with the crane fully supporting the main shaft,horizontally sliding the main shaft out from the bedplate.
 2. The methodof claim 1, wherein the assist system is disconnected from the downwindend of the main shaft before or after the bearing unit is unloaded. 3.The method of claim 1, wherein the assist system is any one orcombination of an electrical, hydraulic, pneumatic, or electro/hydraulicsystem configured in a push mode at the downwind end of the main shaft.4. The method of claim 3, wherein the assist system comprises ahydraulic ram assembly, the method comprising configuring multiplehydraulic cylinders with rams at the downwind end of the main shaft in amanner to apply a uniform pushing force to the downwind end of the mainshaft.
 5. The method of claim 4, wherein the hydraulic ram assemblyincludes a plate that bears directly or indirectly against the downwindend of the main shaft, the hydraulic cylinders and rams configured toapply the pushing force to the plate.
 6. The method of claim 5, furthercomprising fixing a ring to the downwind end of the bedplate around themain shaft, and fixing a rod to the ring for each hydraulic cylinder,the hydraulic cylinders and plate slid onto to the rods in anorientation such that the rams bear against stops on the rods and thecylinders are mounted to the plate.
 7. The method of claim 3, whereinthe main shaft has a main bearing assembly fitted thereon adjacent theupwind end of the main shaft, the assist system having a push strokesufficient to unseat the main bearing assembly and push a center ofgravity of the main shaft and main bearing assembly out from the upwindend of the bedplate.
 8. A method for installing a main shaft andattached main bearing assembly for a wind turbine in a bedplate in thefield, wherein a generator has been removed from the bedplate, themethod comprising: connecting a rigging system to an upwind end of themain shaft, the rigging system suspended from a crane; with the crane,fully supporting and moving the main shaft through the bedplate until adownwind end of the main shaft is positioned at a bearing unit fixed inthe bedplate adjacent the downwind end of the bedplate; and fixing anassist system to the downwind end of the bedplate in a pullconfiguration, and pulling the downwind end of the main shaft from thebedplate until the main bearing assembly fixed to the main shaft isseated in the bedplate, the main shaft supported by the bearing unit asit is pulled by the assist system.
 9. The method of claim 8, wherein therigging system is disconnected from the upwind end of the main shaftafter the main bearing assembly is seated in the bedplate.
 10. Themethod of claim 8, wherein the assist system is any one or combinationof an electrical, hydraulic, pneumatic, or electro/hydraulic systemconfigured in a pull mode at the downwind end of the main shaft.
 11. Themethod of claim 10, wherein the assist system is a hydraulic ramassembly in a pull configuration, the method comprising configuringmultiple hydraulic cylinders with rams at the downwind end of the mainshaft in a manner to apply a uniform pulling force to the downwind endof the main shaft.
 12. The method of claim 11, wherein the hydraulic ramassembly includes a first plate fixed directly or indirectly to thedownwind end of the main shaft, the hydraulic cylinders and ramsconfigured to apply the pulling force to the plate.
 13. The method ofclaim 12, wherein a pull plate is first fixed to the downwind end of themain shaft, the first plate fixed to the pull plate.
 14. The method ofclaim 11, wherein the hydraulic ram assembly has a pull strokesufficient to seat the main bearing assembly in the bedplate.
 15. Themethod of claim 11, further comprising fixing a ring to the downwind endof the bedplate around the main shaft, and fixing a rod to the ring foreach hydraulic cylinder, the hydraulic cylinders and first plate slidonto to the rods in an orientation such that the rams bear against thering and the cylinders are fixed in position by stops on the rods.